1. Field of the Invention
This application relates to a method and a device for showing stereoscopic video images on a display, in particular video images which are obtained in real time when viewing an object through a video stereomicroscope.
2. Description of Related Art
Such methods are known and are associated in practice with a certain outlay in order to ensure that the stereo images reproduced on a monitor are also of satisfactory quality. The fact that it is necessary to display one right-hand and one left-hand partial image each per displayed stereo image gives rise to various image-processing problems, for example that right-hand and left-hand partial images are displayed in the correct sequence on the monitor. DE-C-4134033 specifies such methods, for example in column 4, line 57 to column 5, line 36.
However, it is still not enough purely to display the partial images in the correct position on a monitor. Thus, in particular, the focal length of the two recording devices should also correspond, and devices should be provided which permit a viewer to view the partial images on the monitor. In video stereomicroscopes (surgical microscopes), the problem of focusing is slight whenever use is made of only one objective, through which both video cameras, or else only one video camera with a suitable recording possibility for a right-hand and a left-hand image channel (for example mirror stereoscope basis), are directed.
Also important, moreover, is the viewing quality of the displayed stereo images on the monitor, for which, in addition, physiological factors also play a role. Zoom objectives serve the purpose, for example, of optimum selection and enlargement of an image section; illumination settings permit the object to be illuminated to suit the eye, etc.
However, a problem which has not yet so far been satisfactorily resolved results from the circumstance that the human eyes are always set to a fixed stereobasis, specifically the fixed interoccular distance of the person involved.
Particularly in the case of an enlarged display of objects which are viewed, for example, through a microscope, unnatural stereo effects arise which are caused, inter alia, by the stereobasis, which apparently varies during the enlargement. This even plays a positive role in the neighboring depth of field to the convergence plane, since an apparently enlarged stereobasis produces an improved 3-D effect and the depth of perception at the object being viewed is improved. However, the further away the object details are on the convergence plane, the more unnatural the actually perceived image appears. Since in the regions remote from the convergence plane, above all, the apparent stereobasis no longer at all corresponds to that which the viewer is accustomed to seeing and, in addition, an intensified impression of unsharpness is also produced there (after all, the viewing optical system is focused onto the convergence plane, as a rule), this leads to a taxing additional stress in the viewer's visual apparatus, above all in the brain. This additional stress is sometimes felt as unpleasant, but is sometimes initially not perceived at all. In both cases, however, headache and poor vision can be produced thereby, as a result of which, in particular, the viewing period at such a microscope is distinctly reduced. Apart from this, it is then also possible to detect the relevant regions of the object only with particular difficulty.